This invention relates to the recovery and recycling of photographic and industrial waste materials, and more particularly to a method for recovering metalic silver and plastic base materials used in the production of X-ray and photographic films, and the lie.
The public has become more and more aware of the need for protecting our environment against continued deterioration resulting from the accumulation of industrial and domestic waste in our rivers, streams and fields. In its simplest form, such protective steps have included the practice of requiring each household to separate from its trash recyclable paper, and plastic and glass containers. However, more sophisticated waste products, such as for example exposed or "used" photographic and X-ray films, continue to present a problem for two reasons. The emulsion coatings on such films contain significant quantities of silver, and the plastic sheet material, which forms the substrate for the film's associated emulsion or silver-bearing coating is not biodegradable.
Heretofore, efforts have been made to recover and recycle at least portions of film of the type described, but such prior art efforts have involved rather complicated methods and costly apparatus. For example, U.S. Pat. No. 3,510,413 discloses, generally, the method of mixing and agitating film chips in a liquid bath which is designed to remove the emulsion layer from the plastic chips. Thereafter the chips are separated from the liquid bath, and silver is recovered from the bath via an electrolytic process. However, one disadvantage of such prior art process is that the percentage of recovery of the silver is rather poor, and the silver that is recovered is not of very high purity. The U.S. Pat. Nos. 3,793,168 and 4,093,532 also disclose the use of electrolytic processes for recovering silver from the emulsion residue of photographic film, but again, the purity of the recovered silver is not satisfactory.
There are, of course, other methods of recovering silver from waste or used photographic film and the like, see for example U.S. Pat. Nos. 4,299,676 and 3,929,466, but such processes do not utilize an electrolytic process for recovering extremely pure silver in a manner disclosed hereinafter by applicant.
Accordingly, it is an object of this invention to provide an improved, efficient, readily available and inexpensive method of recycling film products of the type described, thus substantially eliminating any ground or atmospheric pollution, which might otherwise result upon the discard of such products.
Still another object of this invention is to provide an improved, alternative method to the known method of disposing of used film by burning the film, a process which releases toxic chemicals into the air by vaporizing the plastic film substrate.
Another object of this invention is to recover and recycle plastics such as MYLAR and like plastic backings which are utilized by X-ray and photographic film, thus enabling reuse of such plastic in photographic and plastic industries.
Still a further object of this invention is to provide an improved process and apparatus which enables recovery from waste photographic and X-ray film, and the lie, silver which has a purity of approximately 0.999 fine, and whereby no toxic metal is released into the atmosphere.
Also, it is an object of this invention to provide an improved method and apparatus for recovering silver and plastics from used photographic film, and the lie, and which are so effective and safe in handling toxic materials, that the method and apparatus would be perfectly suitable for use by hospitals, clinics, and the like.
Other objects of the invention will be apparent hereinafter from the specification, and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawing.